Deuterium,Oxygen-18 and Salt Content of Drinking Water Sources in Cairo

The contineous increase of population in Cairo exceeding 10 millions inhabitants lead to the search for supplementary potable water resources in addition to the Nile River which is the principle drinking water source. Groundwater represents the main supplementary source. Evaluation of the groundwater feeding the so-called El-America Water Treatment Station which is one of the biggest potable water supplies at the northern of Cairo was carried out. Chemical and isotopic techniques were applied to estimate the suitability of this groundwater for drinking purposes. The chemical analysis includes the determination of sodium, potasium, calcium and magnesium concentrations in addition to those of chlorides, sulphates, bicarbonates and silicates, while the isotopic analysis includes oxygen-18 and deuterium. The overall chemical- and isotopic investigations determined the conditions at which the examined groundwater is suitable for drinking purposes.     

Sulphur and Oxygen Isotopes in Sulphates in Natural Waters: (2) Deep-Waters from Horizons Below Baltic Sea Floor

Abstract

In this paper we consider deep waters from horizons located under the Baltic-Sea bottom. The samples were taken twice from wells bored in Hel peninsula. The δ¹⁸O and δD values of these waters show their glacial origin since they have significantly low values (δ¹⁸O from ?14 to ?11 whereas the modern groundwaters in Gdańsk area have ?10%₀). In contrast to surface waters the sulphates dissolved in these deep waters have rather high and uniform δ¹⁸O values which are correlated with δ¹⁸O of H₂O but not correlated with δ³⁴S. The isotope patterns may be explained assuming that the waters are very old, in which the slow process of oxygen isotope exchange at low temperatures, but extended in time, could enrich the sulphate in heavier oxygen isotopes.     

Fractionation of Oxygen and Hydrogen Isotopes at the Hydrate Gas forming in the Sea Sediments

The paper gives data on isotope composition of interstitial and near-bottom waters sampled in a region of gas-hydrate formation in the Sea of Okhotsk. The studies shows that heavy isotope of oxygen and hydrogen is used in gas-hydrate formation, with the result that isotope composition of its constitution water constitutes δ¹⁸O = +1.99‰, δD = +23‰ relatively to SMOW. Formation of autogenic carbonates leads to isotope exchange with interstitial water wich, in turn, changes its primary isotope composition in the direction of increasing of O-18 content. The near-bottom waters are isotope-light relatively to the SMOW standard and to the mean isotope composition of interstitial water in the studied region of gas-hydrate spreading.     

Origin and Recharge Altitude of the Thermo-Mineral Waters of the Eastern Pyrenees

The thermo-mineral waters of the axial zone of the Eastern Pyrenees form a geochemically homogeneous group. They emerge in granite or orthogneiss and all have a sodium sulphide chemistry. Principal component analysis of their physico-chemical parameters has distinguished three types of fluid, 1) hot water that has evolved in a closed system and whose chemistry may reflect that of deep water, 2) water that is also of unmixed origin, but whose chemical composition has been modified during cooling by conduction, and 3) water cooled by mixing with surface water.

Stable isotope (¹⁸O, ²H) contents indicate that all the waters are of meteoric origin (from oceanic and/or Mediterranean precipitation). No heavy isotope enrichment has been found that would indicate evaporation or a geothermal effect between water and the host rock.

The differences in isotope contents between surface and thermo-mineral waters are attributed to a difference in recharge altitude; altitude gradients in ¹⁸O and ²H, estimated by two independent methods, are respectively 0.24‰ and 1.84° per 100m. They may, however, be lower when precipitation is in the form of snow. Applying these calculated gradients to thermo-mineral waters, taking mixing effects into account, has given an estimate of the minimum altitude of recharge of 110 springs in the Eastern Pyrenees.     

近海面大气光学湍流计算模型的比较与改进

通过在黄海北部某海域进行的海上大气光学湍流观测实验,对比分析了不同大气稳定度环境下四种大气光学湍流C2n计算模型的性能。针对中性和近中性环境下模型误差大的问题,基于温度折射率结构参数fT与稳定度的对应关系,利用实测数据和函数拟合,提出了一个新的fT函数形式。误差分析表明采用新的fT参数方案明显提高了C2n模型的计算精度,其性能大大高于其他几种计算模型。     

Sulphur and Oxygen Isotopes in Sulphates in Natural Waters: (1) Surface Waters of Relatively Unpolluted Terrains

Abstract

The paper presents a whole-year study (1990) of an unique area in S-E Poland with numerous small rivers and streams carrying clean waters. We report the results of δ¹⁸O of waters and δ³⁴S of the sulphates sampled 4 times in 1990 from 20 rivers of the study area. The observations clearly show the impact of biological activity on the oxygen and sulphur isotopic compositions in sulphates. Attempts have been made to interpret the correlation between δ³⁴S and δ¹⁸O in sulphates. The highest correlation coefficient has been noticed for samples collected in April, whereas the lowest in August. The conclusion of this study is that the river sulphates are predominantly produced outside the river environment. We have distinguished three major sources of sulphates: (1) ones produced in the aquifer from which waters are discharged, (2) those produced in soils and marshes of forest environment, and (3) ones on anthropogenic origin.     

Spatial and temporal characteristics of stable isotopes in the Tarim River Basin

By using 233 isotope samples, we investigated the spatial and temporal variations of δ¹⁸O and δ²H in precipitation and surface water, and the contribution of different water sources in the rivers within the Tarim River Basin (TRB), which receives snow/glacier meltwater, groundwater, and rainfall. Our study revealed a similar seasonal pattern of precipitation δ¹⁸O and δ²H at both the north and south edges of the basin, indicating the dominant effect of westerly air masses in the summer and the combined influence of westerly and polar air masses during the winter, although the southern part showed more complex precipitation processes in the summer. River water in the basin has relatively large temporal variations in both δ¹⁸O and δ²H showing a distinct seasonal pattern with lower isotope values in May than in September. Higher d-excess values throughout the year in the Aksu river and the Tizinafu river suggest that water may be intensively recycled in the mountains of the TRB. Based on isotopic hydrograph separation, we found that groundwater is the main water source that discharges the entire basin although individual rivers vary.     

Temporal 18O and deuterium variations in hydrologic components of a small watershed during a typhoon event

The differences between δ¹⁸O and δ²H in throughfall and open rainfall were studied for a selected typhoon event in a watershed within the Taihu Lake drainage basin, eastern China. In this event, the isotopic composition of precipitation exhibited a strong temporal variation. Comparison results show that an isotopic composition difference existed not only between gross rainfall and average incremental rainfall, but also between different calculation methods used to derive average. The differences between incremental precipitation and throughfall isotopic composition were observed in this study. Considering the temporal variation in rainfall and throughfall during this typhoon event, the incremental value can have an effect on hydrograph separation more accurately in evaluating the importance of ‘new’ water. In addition, isotopic fluctuations of surface water and groundwater differed from those of rainfall and throughfall throughout the event.     

Isotope variations of hydrogen,carbon and nitrogen in florae from the Schirmacher Oasis,East Antarctica

Comparative biochemical and isotope-chemical investigations of cosmopolitical plants open up ways of obtaining parameters from different parts of the Earth which are characterised by variations in the habitat due to different environments. As an Antarctic oasis, the Schirmacher Oasis disposes of adequate favourable ecological conditions for the growth of lower plants.

In the present paper, results of isotope studies of lichens, mosses and algae of the Schirmacher Oasis are given and peculiarities of the habitats which influence the isotope contents of the plants are discussed.     

Isotopic composition in precipitation and groundwater in the northern mountainous region of the Central Valley of Costa Rica

The linkage between precipitation and recharge is still poorly understood in the Central America region. This study focuses on stable isotopic composition in precipitation and groundwater in the northern mountainous region of the Central Valley of Costa Rica. During the dry season, rainfall samples corresponded to enriched events with high deuterium excess. By mid-May, the Intertropical Convergence Zone poses over Costa Rica resulting in a depletion of ¹⁸O/¹⁶O and ²H/H ratios. A parsimonious four-variable regression model (r^2?=?0.52) was able to predict daily δ¹⁸O in precipitation. Air mass back trajectories indicated a combination of Caribbean Sea and Pacific Ocean sources, which is clearly depicted in groundwater isoscape. Aquifers relying on Pacific-originated recharge exhibited a more depleted pattern, whereas recharge areas relying on Caribbean parental moisture showed an enrichment trend. These results can be used to enhance modelling efforts in Central America where scarcity of long-term data limits water resources management plans.     

Mathematical Modelling of the Role of Intra- and Extracellular Activity of Carbonic Anhydrase and Membrane Permeabilities of HCO3, H2O and CO2 in 18O Exchange

Abstract

Numerical simulation of ¹⁸O exchange between CO₂, H₂O and HCO₃ ^? explains the ratio mass 46/mass 44 (=C¹⁸O¹⁶O/C¹⁶O₂) measured by mass spectrometry to approximately 1% relative mean difference. In the presence of intact red blood cells the reaction takes place extra- and intracellularly at different reaction rates. Because CO₂ hydration/dehydration is accelerated intracellularly by carbonic anhydrase, a difference in intra- and extracellular concentration of labelled reactants occurs. The ensuing transfer of reactants across the cell membrane depends on their membrane permeabilities which are approximately P_{CO 2} ? 2 cm/s, P_{H 2 O} ? 0.002 cm/s and P_{HCO 3} ? 0.00015 cm/s (values from the literature). We found that the numerical simulation is affected most by P_{HCO 3} . The influence of the other permeabilities is at least ten times less. Therefore within the range of normal literature values, P_{HCO 3} is the only permeability that has a rate limiting effect on ¹⁸O exchange. This is why, in turn, P_{HCO 3} can be derived from an experimentally determined time course of mass 46/mass 44 by a fitting procedure. Another crucial parameter that can be estimated from the experimental results is the intraerythrocytic carbonic anhydrase activity A_i .     

Seasonal variation of oxygen-18 in precipitation and surface water of the Poyang Lake Basin,China

Based on the monthly δ¹⁸O value measured over a hydrology period in precipitation, runoff of five tributaries and the main lake of the Poyang Lake Basin, combined with hydrological and meteorological data, the characteristics of δ¹⁸O in precipitation (δ¹⁸O_PPT) and runoff (δ¹⁸O_SUR) are discussed. The δ¹⁸O_PPT and δ¹⁸O_SUR values range from?2.75 to?14.12 ‰ (annual mean value=?7.13 ‰ ) and from?2.30 to?8.56 ‰, respectively. The seasonal variation of δ¹⁸O_PPT is controlled by the air mass circulation in this region, which is dominated by the Asian summer monsoon and the Siberian High during winter. The correlation between the wet seasonal averages of δ¹⁸O_SUR in runoff of the rivers and δ¹⁸O_PPT of precipitation at the corresponding stations shows that in the Poyang Lake catchment area the river water consists of 23% direct runoff (precipitation) and 77% base flow (shallow groundwater). This high proportion of groundwater in the river runoff points to the prevalence of wetland conditions in the Poyang Lake catchment during rainy season. Considering the oxygen isotopic composition of the main body of Poyang Lake, no isotopic enrichment relative to river inflow was found during the rainy season with maximum expansion of the lake. Thus, evaporation causing isotopic enrichment is a minor component of the lake water balance in the rainy period. During dry season, a slight isotopic enrichment has been observed, which suggests a certain evaporative loss of lake water in that period.     

Stable isotope signatures of meteoric water in the Cuvelai-Etosha Basin,Namibia: Seasonal characteristics,trends and relations to southern African patterns

ABSTRACT

The study area is the Namibian part of the Cuvelai-Etosha Basin (CEB), located in central northern Namibia. The CEB is home to 40 % of Namibia’s population, and most of the people live in rural areas. These people depend on both surface and groundwater resources which are limited in this dryland (mean annual rainfall ranging from 250 to 550?mm/a). The isotopic signatures of δ¹⁸O and δ²H from water samples (n?=?61) collected over a course of 9 years from various research projects and existing (but mainly unpublished) data of meteoric water of the CEB (10 sites) were evaluated and local meteoric water lines (LMWLs) developed. Further, the data is discussed in the context of seasonal characteristics and trends and compared to available data from the Global Network of Isotopes in Precipitation (GNIP) for the southern African region. Our results extend the portfolio of previously published LMWLs for southern Africa and provide a more precise baseline for any isotope-based study in that region. The slope of the LMWL from the GNIP stations correlates with latitude. This correlation cannot be found within the CEB. The dominant control on the isotopic signature of the CEB of precipitation is seasonal.